Asymmetric Pentacene Derivatives for Organic Light-Emitting Diodes

Two aryl-substituted red emitting pentacenes, 5,6,13,14-tetraphenylpentacene (asym-TPP) and 5,14-bis(2,6-dimethylphenyl)-6,13-diphenylpentacene (DMPDPP), have been prepared and spectroscopically characterized. Guest−host films of pentacene derivatives dispersed in tris(quinolin-8-olato)aluminum(III) (Alq3) exhibit narrow red emission (λmax = 663−680 nm), indicative of efficient Förster energy transfer from the Alq3 host to the guest molecules. Solid-state absolute photoluminescence quantum yields of the films were measured as a function of guest molecule concentration (ΦPL ∼20% at 0.20−0.50 mol %). Red light-emitting diodes based on the fluorescent DMPDPP yield external electroluminescence quantum efficiency (ηEL ∼1%) close to the theoretical limit.